Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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FXUS64 KHGX 160225

Area Forecast Discussion
National Weather Service Houston/Galveston TX
925 PM CDT Sat Jul 15 2017

Convection continuing to move off to the SW this evening with
skies slowly clearing in its wake. Did make some minor tweaks
with the the overnight forecast, mainly to account for the el-
evated PWs and likelihood of redevelopment overnight with the
next s/wv moving in from the NE. 41


.PREV DISCUSSION...  /ISSUED 412 PM CDT Sat Jul 15 2017/

The combination of a passing of a weak upper level disturbance
over a lower level boundary between the Sabine River Valley and
Galveston Bay...all within a very moist unstable tropical air
mass...lit the fuse to a very active day of clustering showers and
storms. Discrete cells galore moving at around 20-25 mph to the
southwest within the northeasterly steering flow. As has been the
case this month...downstream cell propagation has not been impeded
by rain-cooled air put out by earlier activity. Although many of
these discrete cells have not reached severe thresholds...the
majority of them have produced high instantaneous rain rates that
have led to radar-estimated 1 to 2 inch per hour amounts with
their passing. Many Houston area guages have picked up between
near an inch to around 2.5 inches of rain in the past 6 hours.
Wind gusts of around 40 mph have been recorded...nuisance flooding
of roadways and one report of a lightning injury in Montgomery
County. Thinking is that once this shortwave disturbance rotating
around Intermountain West ridging passes west-southwest of the
region this evening...activity will come to a close with the
setting sun. Any lingering thunderstorms will likely be focused
over the coastal counties and points offshore within the Gulf.

This wet pattern will be hanging on through early next week. An
inverted trough will be forming in the height field just south of
Plains ridging and eastern CONUS troughing tomorrow. This will
will promote a regeneration of regional storm activity. High PW
air of between 1.9 to 2.1 inches with (over) 7 deg C sfc-3 km
lapse rates and 86-89F convective temperatures all lean this
forecast more wet than dry through mid-July. All of the ingredients
are in place for return periods of rain and thunder...with early
day coastal development leading to late morning through early
evening inland county action. The resident air mass is moist and
unstable enough to support ordinary thunderstorm initiation and
development that will exhibit slow storm motion within a weakly-
sheared column. Models advect in early work week higher PVA within
easterly flow underneath an eastward expanding Southern Plains
ridge. With little to no change in the regional thermo-moisture
profile...all that is required will be a little lift to (re)generate
discrete cells capable of producing bursts of lightning...winds
to 40 mph in gusts...funnels or weak tornadoes and 1 to near 3
inch per hour rain amounts within the strongest cells. Generally...
early day Gulf activity will begin over the maritime and then
fester further inland through the daytime morning hours. Dependent
upon what the early day activity spits in the form of outflow
boundaries will determine where afternoon convection blossoms
and clustering will center.

The only mentionable item in the extended will be that upper
ridging will envelop the southeastern U.S. at week`s close. This
particular height pattern will only reinforce a lower-middle
level flow pattern that would bring northern Gulf disturbances
right into eastern Texas. 12Z Global models show no hint of any
type of Gulf tropical activity. The theme word will continue to
remain `unsettled` with return bouts of daytime showers and
thunderstorms...a degree or two fluctuation in the diurnal
temperature field. 31


College Station (CLL)      77  95  75  93  75 /  20  40  20  70  30
Houston (IAH)              75  92  76  91  76 /  20  50  20  80  40
Galveston (GLS)            81  89  80  88  80 /  40  40  30  70  50



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